The present invention relates to ball valves, and, more particularly, to ball valves for use with high temperature and/or high pressure fluids.
Ball valves have wide application in the control of fluids in various industrial applications. Such valves generally have a spherical ball with a passage extending therethrough which allows fluid flow through the valve when the valve is open. When the valve is closed by rotating the ball, valve seats about the flow passage in the housing seal against the surface of the ball member to preclude fluid flow through the valve.
Under less demanding operating conditions, various metal alloys may be selected for the components so that the valve will exhibit long life without need for frequent replacement of parts. However, valves used in applications involving high pressure particularly in combination with high temperature and/or highly corrosive fluids, such as encountered in the utility and chemical process industries, exhibit a relatively short useful life because of erosion of the valve components, particularly in the area about the valve seats and in the flow passages. Eventually, this erosion will require removal of the entire valve from the line and replacement.
To facilitate inline service without necessitating removal of the entire valve assembly from its operational environment, some valve bodies have been designed with an opening which permits the ball member and valve seats to be removed. Commonly referred to as a top entry ball valve, this type of ball valve is illustrated in Canuet et al U.S. Pat. No. 4,802,652.
However, there remains a need for ball valves which not only are easy to repair, but also long lived in operation without frequent parts replacement.
It is an object of the present invention to provide a novel ball valve in which erosion is reduced.
It is also an object to provide such a ball valve in which the valve seats may be readily removed and replaced.
Another object is to provide such a ball valve in which the valve seats are movable between the valve body and ball member to accommodate dimensional variations and to ensure good sealing action with the ball member.
Yet another object is to provide such a ball valve employing novel valve seat inserts which are urged against the ball member.
A further object is to provide such a ball valve with a highly effective bonnet/valve stem seal.